Why Is the Angular Velocity of a Clockwise-Spinning CD in the -y Direction?

[Qnslaught]

Homework Statement

A CD player spins a disc in a clockwise direction when looking at the player from the top. What is the direction of the angular velocity.

Homework Equations

The Attempt at a Solution

OK, the key for this practice exam says the answer is in the -y direction. I used the right hand rule to see that the direction is negative, but I thought it would be in the -z direction. Can someone explain why it is -y?

 

[SeanGillespie]

I believe they have made the answer this way as you are only using two dimensions. If you take the vertical y-axis as the axle for the rotation, your right thumb will be pointing in the negative y-direction when you use the right hand rule.

 

[kerimek]

As a scientist, it is important to understand the conventions used in describing angular velocity. In this case, the direction of angular velocity is determined by the right hand rule, where the direction of rotation is given by the direction of the curled fingers when the thumb points in the direction of the axis of rotation. In this case, the axis of rotation is perpendicular to the CD player, and since we are looking at it from above, the thumb points in the -z direction. However, the convention for assigning directions in a 2D plane, such as the top view of the CD player, is to use the -y direction as the positive direction and the +y direction as the negative direction. Therefore, the angular velocity in this scenario is in the -y direction, as indicated by the answer key. It is important to keep in mind the conventions and coordinate systems used when analyzing physical systems.